With the rapid deployment of the 3rd Generation (3G) network, the operators need to reduce costs of network construction and operation. The Next Generation Mobile Network (NGMN) association of operators brings forward requirements on management simplicity and cost efficiency, and summarizes such requirements on Self-Organizing Networks (SON) in a number of operator use cases.
Currently, automation configuration of PCI is important for work reduction for wireless operators in a Long Term Evolution (LTE) system. PCI is used for uniquely identifies a cell in a network. Each cell is assigned an available PCI. A basic principle for allocating the PCIs among cells is to be collision-free and confusion-free. Communication is impossible within cells with a conflicted PCI, as the User Equipment (UE) can not detect or differentiate the cells.
However, the number of PCIs allocable in the entire communication is a limited constant. Based on the LTE specification of the physical layer detailed in 3GPP TS 36.211-840, there are a total of 504 unique PCIs. These PCI are grouped into 168 unique physical layer cell identity groups, where each group contains three unique identities. In contrast, a typical commercial network may have 300 sites/base stations, assuming three sectors per site leads to almost a thousand cells. In the practical LTE network, it is necessary to multiplex or reuse such PCIs. The number of cells in the system is still increasing dramatically. For example, three sector base stations are large-scale deployed in Korea by now, but operators have decided to deploy more six sector base stations in future. In addition, micro base stations (also known as femto base stations) are additionally installed to optimize coverage and capacity. It is necessary to efficiently multiplex or reuse the PCIs while preventing the possible conflicts.
Typically operators use an offline planning tool or depend on manual determination to develop a PCI deployment plan. The plan uses basic information such as eNodeB location, potential neighbors, etc., to determine the PCI for each eNodeB/sector. Such an allocation is carefully reviewed to ensure that the network does not have any PCI conflicts. The determined PCI values are communicated to each eNodeB during the installation using the configuration files or manually inputted by the staff. It is no doubt that such a process does not lend itself to subsequent changes and is prone to human error.
3GPP TS 36.902 (Release 9) describes the case of PCI allocation. It only denotes the target that system can select a PCI for a newly deployed radio cell and requires that the PCI assignment shall be collision-free and confusion-free. However, it does not propose any solution for implementing the PCI allocation.
CN 101990210A proposes a method to divide PCIs into two consecutive aggregates. One of them is for macro cells and another one is for micro cells, and the cell radius is only a typical value which has risk to avoid PCI conflict. However, this method still needs operators to plan network at first. It doesn't mention any methods to implement auto configuration.